The present application claims priority to Japanese Patent Applications No. 2001-228480 filed Jul. 27, 2001, No. 2001-346096 filed Nov. 12, 2001, and, No. 2001-361399 filed Nov. 27, 2001, the entirety of each is hereby incorporated into the present application by this reference.
The present invention relates to a method for manufacturing by molding an automobile interior article body (or a hard resin body) in which an automobile interior article having a cover portion being developed from which an airbag inflates is integrally molded of a hard resin material.
The invention will be described hereinafter mainly in connection with an instrument panel (hereafter abbreviated to xe2x80x9cpanelxe2x80x9d) having a cover portion for an airbag. However, the invention can also be applied to cover portions for airbags for side doors, pillars and front/back seats.
In the so-called xe2x80x9chard panelxe2x80x9d (the usual injection-molded panel), the body of which is molded of a hard resin (e.g., PPF), a bag covering member formed at the pop-out port of the passenger""s seat airbag is molded in the prior art separately from the panel body. Therefore, a gap or abrupt shift in the surface is easily formed between the bag covering member and the panel body so that restrictions must be placed on the design, increasing the number of assembling steps.
Therefore, there has been proposed (as referred to FIGS. 4 and 5 of Unexamined Published Japanese Patent Application No. 71924/2000) a hard panel which is constructed to comprise: a hard resin body (or a panel body) having an integrally molded cover portion; and a soft resin connector (or an airbag supporting assembly) jointed to the rear side of the cover portion and assembled with an airbag module.
Moreover, the cover portion of the panel or the hard resin body is required to have grooves or notches to be broken, so that the cover may be broken when the airbag is activated.
These grooves or notches are formed by a high-frequency welder or a laser working after the panel body is injection-molded. However, the formations of the grooves or notches are done after the molding so that the number of steps increases. Moreover, it is difficult to control the breaking positions and depths, and costs rise as a result.
Therefore, a technique for forming the broken groove portions (or the notch portions) by stamping a groove forming projection just after the end of injecting has been proposed (in Unexamined Published Japanese Patent Applications No. 268205/1996, No. 254919/1991 et al) in pads for steering wheels (molding of a soft resin material).
In case this technique is applied to a hard panel (or an automobile interior article body) made of a hard resin material, however, it has been found that extrusion marks due to the pushing of the groove forming projection (or the groove forming block) appear on the surface of the molding (design face), a problem which does not occur in the case of soft resin material. It is hypothesized that the pushing pressure is harder for hard resin material to absorb than the soft resin material.
In view of the foregoing background, the present invention has an object to provide a method for die-molding an automobile interior article body to which a cover portion being developed from which an airbag inflates is integrally molded of a hard resin material and in which no extrusion marks caused by pushing of the tear-line forming projection appear on the surface side.
In order to solve the aforementioned problem, we have keenly pursued promising developments and have found that the problem can be solved if the stamping of the tear lines is done during the time between just after the material filling (or injection) to the end of filling, and to conceive a method for manufacturing the above automobile interior article having the construction as described below.
According to a mode of the invention, there is provided a method for die-molding with a hard resin material an automobile interior article incorporating integrally a cover portion being developed from which an airbag inflates, wherein the cover portion is also molded of a hard resin material integrally with the other portions, and wherein a tear line forming block having continuous or discontinuous tear line forming protrusions corresponding to the tear lines for the cover portion is moved forward at the molding step during the time between just after the start of mold filling to the end of filling to form the tear lines.
While the molding material is being filled, its fluidity is so excellent that extrusion marks therefore hardly appear at all in the design surface.
This effect is attained more reliably if the forward movement of the tear line forming block is done in one half of the time taken for filling of the molding material.
It is usual that the forward movement of the tear line forming block is done in {fraction (1/10)} to xc2xd of the mold filling time.
Alternatively, at the time of the forward movement of the tear line forming block, the temperature of the mold at its face forming the outer side of the molding, opposite to the tear line forming block, may be higher than that of the tear line forming block. The cooling and hardening from the outer side can thus be suppressed to reduce the resistance of the material to the stamping during tear line forming.
More specifically, the molding temperature of the mold at its face forming the outer side of the molding opposite to the tear line forming block is kept between the thermal deforming temperature (ASTMD648: 455 k Pa) and the melting temperature till just after the completion of the forward movement of the tear line forming block.
In this construction, moreover, it is desired that the backward movement of the tear line forming block is completed before the mold opening. If the backward movement of the tear line forming block is done after the mold is opened, the drawing resistance of the tear line forming projection is so high that the surface appearance will probably be affected.
In this construction, it is desired that the backward movement of the tear line forming block of the tear line forming projections is done at a plurality of steps. In this way the shape of the tear line forming holes is stabilized. If the tear line forming block is moved backward at an early time, for example in one step while pressure is being applied, the material at the opening of the holes forming the tear line still has fluidity so that there is a possibility it will flow in the direction to close the opening of the tear line forming holes and set in that shape. At a late time just before the mold opening or just before the completion of the cooling time, on the other hand, the drawing resistance of the tear line forming projection is lower than the aforementioned one but may cause a similar problem.
Among the steps of the backward movement of the tear line forming block, the first one usually is during the mold pressurizing time and the last one during the mold cooling time. It is desired that the first and last steps of the backward movement of the tear line forming block are done in {fraction (1/10)} to xc2xd of the mold pressurizing time and for xc2xd to {fraction (9/10)} of the mold cooling time, respectively. Moreover, if the backward movement of the tear line forming block is done in two steps, the backward stroke of the first step is {fraction (1/10)} to xc2xd of the whole stroke.
In the individual constructions thus far described, moreover, it is desired the tear line forming projections are made of a set of conical or frustoconical pins. The material flow is smoothed, and the leading ends of the individual pin holes to be formed by the tear line forming projection are tapered to facilitate the stress concentration and to stabilize the cover portion expandability.
Another object of the invention is to provide a surface portion thermal molding method for thermally molding (or vacuum molding) the surface portion of an automobile interior article having a portion for covering an airbag, suppressing rise in cost and reliably breaking off at tear line portions (portions to be broken). This object can be achieved by the following individual construction.
There is provided a method for thermally molding a surface portion in an automobile interior article having a cover portion enabling an airbag to pop out, wherein surface tear lines on the cover portion are formed simultaneously with the thermal molding of the cover portion, wherein the thermal molding includes a preliminary shaping by a press molding using a pair of male/female dies and a later final shaping by a vacuum molding simultaneous with the die closing, and wherein the vacuum molding is done in the female die, and at the vacuum suction time of the vacuum molding, tear line forming blades embedded in the male die are moved forward and backward to form surface tear lines in the rear face of the surface portion.
After the preliminary shaping by the press molding, the surface portion material is shaped through close contact with the front surface shaping face (the female die shaping face) caused by the vacuum suction so that the nonuniformity of thickness and the poor reproduction of the surface (the design bearing face) can be avoided, unlike shaping with only vacuum molding.
Because of the vacuum molding (or vacuum suction) by the female die, moreover, the die release (or die releasability) after the molding completion is better than the case of the vacuum molding by the male die, which improves the productivity.
Automobile interior article surface portions are extremely thin (e.g., 2 mm or less at most, usually 0.5 to 1.0 mm) so that if groove portions to be broken (or the fragile portions to be broken) are provided, the release from the mold is difficult or is accompanied by breakage of the surface portion.
Moreover, the surface portion tear line portions are formed by protruding the tear line forming blade during the vacuum molding (or at the vacuum suction time), when the surface portion material is still at a thermally deformable temperature, so that the stamping pressure can be low. Even if the surface portion extrusion marks are temporarily formed on the surface, they are leveled (or smoothed) by the vacuum forming to leave no trace of the tear line forming process on the surface.
In the construction described above, it is desired that the temperature (the tip temperature) of the blade (the groove forming blade or projection) the tear line forming blade is higher than the melting temperature of the rear side of the surface portion. The groove portions to be broken are curved (smoothed) on the bottom, all with an equal depth, and not affecting the design on the surface (design face). Specifically, the surface portion tear line portions (or grooves) are formed at the vacuum suction time so that the surface portion material easily escapes. When the grooves are to be thermoplastically deformed by the tear line forming blades (the groove shaping projections), there tends to be much variation in the degree of penetration so that there is much variation in groove depth thereby and also there is formation of ridges along the grooves on the design face side. If slits (or cut grooves) having an extremely small width are formed with the groove forming blade, moreover, there is similar variation in groove depth according to the sharpness of the blade. The variation in the groove depth may easily cause a difference in the breaking characteristics of the grooves to be broken.
The method of molding the automobile interior article of the aforementioned construction employs a thermal mold having the following construction.
There is provided a thermal mold used in a method for thermally molding not only a surface portion in an automobile interior article having a cover portion being developed from which an airbag inflates but also a surface portion tear line portion of the cover portion simultaneously, comprising: a female die for vacuum molding; and a male die for acting with the female die for a press molding, wherein the male die includes a tear line forming blade made movable outward from the face of the male die and also movable to its original position.
In case the surface portion tear line portions (or the portions to be broken) are made of molten grooves, moreover, the tear line forming blade includes heating means for heating an edge portion locally to the melting temperature of the surface portion or higher.
Moreover, the surface portion molded by the aforementioned thermal molding method has the following construction.
There is provided a surface portion in an automobile interior article having a cover portion being developed from which an airbag inflates, comprising a surface portion tear line portion formed in the cover portion on the rear side, wherein the surface portion tear line portion is formed of continuous or discontinuous molten grooves.
Further, the automobile interior article using the aforementioned surface portion has the following construction.
There is provided an automobile interior article comprising a cover portion being developed from which an airbag inflates, wherein cover portion includes a foamed layer between a cover portion substrate and a surface portion having a surface tear line in the cover portion on the rear side, and wherein the surface tear line is formed of molten grooves.